Field of the Invention
The present invention relates to a display apparatus which can control an intensity of irradiation light which is irradiated onto a display panel and to a controlling method of the irradiation light.
Description of the Related Art
In recent years, a liquid crystal display apparatus having a backlight using a light emitting diode (hereinbelow, referred to as “LED”), as a light source, which is excellent in a light emitting efficiency and a service life has been widespread. In the LED, since an individual difference, an aging degradation, a thermal degrading, and the like are large, in order to control a light emitting amount to a uniform constant value, such feedback control that the light emitting amount of the LED is detected by using a photo sensor provided near the LED and the light emitting amount of the LED is corrected based on a difference between a detected value and a target value has been devised.
However, in the case where the liquid crystal display apparatus in which such feedback control is made is used outdoors, since the photo sensor receives environmental light (hereinbelow, referred to as “external light”) which passed through a liquid crystal panel, an intensity of irradiation light which is irradiated onto the liquid crystal panel from a light source cannot be detected at a high precision. Therefore, the intensity of the irradiation light which is emitted from the LED cannot be properly corrected. The Japanese Patent Application Laid-Open No. 2008-9090 discloses a method whereby a light emitting amount of a light source and an intensity of external light are respectively detected and an influence of the external light is eliminated from a detected value of a light emitting amount, thereby correcting the light emitting amount. The Japanese Patent Application Laid-Open No. 2013-164561 discloses a method whereby when an intensity of external light is small to such an extent that it does not exert an influence on a detected value of a photo sensor, a light emitting amount of a light source is corrected.